In Just for Sidekicks, it is also shown that ponies can and will accept gems as an alternative form of currency in place of bits. Even one tiny, ruby-colored gem was enough for the Cutie Mark Crusaders to purchase a large, industrial-sized pet dryer. In the same episode, Zecora donates a gem to a Filly Guide charity, and Spike is forced to use several gems to pay a bribe, get onto the Friendship Express train, and as compensation for food the pets ate. In Rarity Takes Manehattan, Rarity tips a hotel bellhop with gems and insists that he keep the change.

Other

Gems feature prominently in this episode. Rarity runs out of gems for her outfits, and goes searching for them with Spike. She uses a magic spell to locate gems, and Spike digs them out. When they're finished collecting gems, the Diamond Dogs appear and tell Rarity that they "hunt for gems", then kidnap her and force her to find gems for them in their vast underground tunnel system. Spike recruits the other ponies' help, and they eventually find Rarity and leave with several cart-loads of gems, which Spike happily dines on.

A special kind of gem which Spike and Rarity identify as a Fire Ruby plays a special role in this episode. Spike shows his heart-shaped Fire Ruby to Twilight and tells her he's been aging it to eat it on his birthday. When Rarity sees it, she dotes on it, and Spike lets her keep it. Rarity makes a necklace out of it for herself and wears it throughout the episode. After Spike turns gigantic because of his greed, he kidnaps Rarity, who doesn't recognize that it's the same Spike. He tries to steal the gem from Rarity, but she holds on to it and describes how generous is the dragon who gave her the gem. Spike has a flashback to the moment he gave Rarity the gem, and shrinks back to his normal size.

After Spike gives Rarity the Fire Ruby, Pinkie Pie tells Spike that Mr. and Mrs. Cake have a "special surprise" for him since it's his birthday. When he enters Sugarcube Corner, the Cakes present him with a blue cupcake studded with sapphires.

The amulet around Trixie's neck has the gem that is the heart of its power.

A red diamond-shaped gem is seen on the Alicorn Amulet, a powerful necklace that gave Trixie a lot of magic power. The power of the gem in this episode is used to defeat Twilight in a "Magic Duel". After Twilight finds out Trixie used the Alicorn Amulet to win, she challenges her to another duel using a fake amulet given to her from Zecora, and the help from her friends. After Twilight beats Trixie in the duel, Trixie takes Twilight's fake amulet. Rainbow Dash then takes the Alicorn Amulet and Trixie attempts to attack Rainbow Dash with her magic, but shortly Trixie learns that the amulet that Twilight had was actually a doorstop from Zecora's house.

Spike's appetite for gems drives the plot for this episode. After he accidentally eats all the gems meant for a jewel cake he was mixing, Fluttershy happens to drop by to ask him if he can pet sit Angel, while she and the rest of the Mane 6 are away at the Crystal Empire, and offers a large green gem as payment. Seeing this as the perfect opportunity to replace the ingredients he ate, Spike offers to look after the pets of the others, in exchange for a gem from each owner. However, as his preoccupation with his future jewel cake takes up most of his thoughts, he doesn't take care of the pets as well as he said he would. This irresponsibility causes him to lose his gems one by one as payment for various mishaps, until he only has half of Fluttershy's gem left. He then, ironically, accidentally devours it too when he meant to drop it into his cake batter.

In a flashback, Twilight Sparkle spends an entire afternoon arranging one of Rarity's gem drawers. Later in the episode, Twilight's friends incorporate memory-depicting gems in a chandelier made from the roots of the Golden Oak Library.

At the Grand Equestria Pony Summit, Princess Cadance dedicates a statue made of gems from each summit delegate's represented city. Later in the episode, Spike also eats a bowl of rubies and a tray of bejeweled cupcakes.

Spike brings Rarity's fire ruby from Secret of My Excess with him on the journey to save her from the Nightmare Forces, wearing it on a cord around his neck. During a lucid nightmare induced by Nightmare Rarity, he shows it to the unicorn, asking if she recognizes it; she doesn't, citing it as not being her color, confirming Spike's fears that she isn't the real Rarity. Following Spike's capture, Shadowfright shatters the ruby, though Spike later retrieves the fragments during his escape. At the end of the story arc, the ponies use their memories of Rarity to restore her, and the ruby's integrity is restored in the process.